1985 Mercury Marquis DASH REMOVAL

Disconnect the battery ground cable.
Drain the coolant from the system.
Disconnect the heater hoses from the heater core tubes. Plug the tubes to prevent leakage.
Disconnect the control system vacuum hose from its source, then push the hose and grommet into the passenger compartment.
Remove the one bolt located beneath the wiper motor that attaches to the left side of the plenum to the dash. Remove the nut that retains the upper left corner of the heater case.
Remove the glove compartment.
Loosen the right door sill plate, and remove the right side cowl trim panel.
Remove the attaching bolt on the lower right side of the instrument panel.
Remove the instrument panel pad. There are five screws attaching the lower edge, one screw on each outboard end, and two screws near the defroster openings.
Disengage the temperature control cable from the top of the plenum. Disconnect the cable from the temperature blend door crank arm.
Remove the clip attaching the center register bracket to the plenum, and rotate the bracket up to the right.
Unplug the vacuum harness at the multiple connector near the floor duct.
Disconnect the white vacuum hose from the vacuum motor.
Remove the two screws attaching the passenger's side air duct to the plenum. It may be necessary to remove the two screws which attach the lower panel door vacuum motor to the mounting bracket to gain access.
Remove the one plastic fastener retaining the floor air distribution duct to the left end of the plenum, and remove the duct.
Remove the two nuts from the lower flange of the plenum.
Move the plenum rearward, then rotate the top of the plenum down and out from under the instrument panel.
Once the plenum is removed, remove the heater core cover and remove the heater core.

To install:

Install the heater core and cover in the proper position.
Position the plenum under the instrument panel.
Install the two on the lower flange of the plenum.
Install the air distribution duct at the left end of the plenum.
Install the two screws attaching the passenger's side air duct to the plenum.
Connect the white vacuum hose at the vacuum motor.
Fasten the vacuum harness at the multiple connector near the floor duct.
Install the clip attaching the center register bracket to the plenum.
Connect the temperature control cable at the top of the plenum and the temperature blend door crank arm.
Install the instrument panel pad.
Install the attaching bolt on the lower right side of the instrument panel.
Install the right side cowl trim panel and door sill plate.
Install the glove compartment.
Install the one bolt located beneath the wiper motor that attaches to the left side of the plenum to the dash. Install the nut that retains the upper left corner of the heater case.
Install and connect the control system vacuum hose.
Connect the heater hoses at the heater core tubes.
Fill the cooling system.
Connect the battery ground cable. Check system for proper operation.